1. Field of the Invention
This invention relates to multiple component meltblown fibers, multiple component meltblown fiber webs, and composite nonwoven fabrics that include multiple component meltblown fibers. The meltblown webs of the invention can be incorporated in composite fabrics suited for use in apparel, wipes, hygiene products, and medical wraps.
2. Description of Related Art
In a meltblowing process, a nonwoven web is formed by extruding molten polymer through a die and then attenuating the resulting fibers with a hot, high-velocity gas stream. In the production of a web comprised of meltblown fibers, it is sometimes desirable to form the fibers from more than one polymeric material where each material can have different physical properties and contribute different characteristics to the meltblown web. A conventional way to form such fibers is through a spinning process where the polymeric materials are combined in a molten state within the die cavity and are extruded together as a layered multicomponent polymer melt through a single spin orifice, as described in U.S. Pat. No. 6,057,256, which discloses the meltblowing of side-by-side bicomponent fibers onto a collector to form a coherent entangled web.
However, this method has significant limitations due to the compatibility constraints placed on the selection of the polymeric materials such that they will spin well together.
Meltblown fibers have been incorporated into a variety of nonwoven fabrics including composite laminates such as spunbond-meltblown-spunbond (xe2x80x9cSMSxe2x80x9d) composite sheets. In SMS composites, the exterior layers are spunbond fiber layers that contribute strength to the overall composite, while the core layer is a meltblown fiber layer that provides barrier properties.
There is a need to provide a new method for forming meltblown fibers, and corresponding meltblown webs, that is more suitable for producing multiple component meltblown fibers, and in which the processing conditions for each polymeric component can be optimized individually.
The present invention is directed to a process for forming a multiple component meltblown fiber comprising extruding a first melt-processable polymer through a first extrusion orifice, simultaneously extruding a second melt-processable polymer through a second extrusion orifice, fusing said first and second melt-processable polymers into an extruded composite filament after extrusion, and pneumatically attenuating said extruded composite filament with at least one jet of high velocity gas so as to form said multiple component meltblown fiber. The composite filament may be broken by the jet of high velocity gas to form a plurality of fine discontinuous multiple component meltblown fibers.
A second embodiment of the present invention is directed to an extrusion die for meltblowing molten polymers comprising at least two separate polymer supply ports entering from an entrance portion of the die, said polymer supply ports communicating with separate extrusion capillaries having exit openings at an exit portion of the die, said extrusion capillaries cooperating as a combined orifice, at least one gas supply port entering from the entrance portion of the die, said gas supply port communicating with at least one gas jet extending through the die and said at least one gas jet arranged concentrically around the exit openings of said combined orifice, wherein said extrusion capillary exit openings and said gas jets communicate with a blowing orifice in the exit portion of the die.
In a third embodiment, the present invention is directed to an extrusion die for meltblowing molten polymers comprising a row of die orifices each comprising at least two separate polymer supply ports entering from an entrance portion of the die, each of said polymer supply ports communicating with separate extrusion capillaries having exit openings at an exit portion of the die, gas supply ports entering from the entrance portion of the die and arranged laterally to said polymer supply ports, said gas supply ports communicating with gas jets extending through the die and arranged laterally to the exit openings of said extrusion capillaries, wherein said extrusion capillary exit openings and said gas jets communicate with a blowing orifice in the exit portion of the die.